/*
 *
 * Licensed to the Apache Software Foundation (ASF) under one
 * or more contributor license agreements.  See the NOTICE file
 * distributed with this work for additional information
 * regarding copyright ownership.  The ASF licenses this file
 * to you under the Apache License, Version 2.0 (the
 * "License"); you may not use this file except in compliance
 * with the License.  You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */
package org.apache.hadoop.hbase.zookeeper;

import org.apache.hadoop.hbase.Abortable;
import org.apache.yetus.audience.InterfaceAudience;
import org.apache.zookeeper.KeeperException;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

import org.apache.hadoop.hbase.shaded.protobuf.ProtobufUtil;
import org.apache.hadoop.hbase.shaded.protobuf.generated.ZooKeeperProtos;

/**
 * Tracker on cluster settings up in zookeeper.
 * This is not related to {@link org.apache.hadoop.hbase.ClusterStatus}. That class
 * is a data structure that holds snapshot of current view on cluster. This class
 * is about tracking cluster attributes up in zookeeper.
 */
@InterfaceAudience.Private
public class ClusterStatusTracker extends ZKNodeTracker {
    private static final Logger LOG = LoggerFactory.getLogger(ClusterStatusTracker.class);

    /**
     * Creates a cluster status tracker.
     *
     * <p>After construction, use {@link #start} to kick off tracking.
     *
     * @param watcher   reference to the {@link ZKWatcher} which also contains configuration and
     *                  constants
     * @param abortable used to abort if a fatal error occurs
     */
    public ClusterStatusTracker(ZKWatcher watcher, Abortable abortable) {
        super(watcher, watcher.getZNodePaths().clusterStateZNode, abortable);
    }

    /**
     * Checks if cluster is up.
     *
     * @return true if the cluster up ('shutdown' is its name up in zk) znode
     * exists with data, false if not
     */
    public boolean isClusterUp() {

        /********
         * TODO_MA 马中华 https://blog.csdn.net/zhongqi2513
         *   注释：
         */
        return super.getData(false) != null;
    }

    /**
     * Sets the cluster as up.
     *
     * @throws KeeperException unexpected zk exception
     */
    public void setClusterUp() throws KeeperException {
        byte[] upData = toByteArray();
        try {
            ZKUtil.createAndWatch(watcher, watcher.getZNodePaths().clusterStateZNode, upData);
        } catch(KeeperException.NodeExistsException nee) {
            ZKUtil.setData(watcher, watcher.getZNodePaths().clusterStateZNode, upData);
        }
    }

    /**
     * Sets the cluster as down by deleting the znode.
     *
     * @throws KeeperException unexpected zk exception
     */
    public void setClusterDown() throws KeeperException {
        try {
            ZKUtil.deleteNode(watcher, watcher.getZNodePaths().clusterStateZNode);
        } catch(KeeperException.NoNodeException nne) {
            LOG.warn("Attempted to set cluster as down but already down, cluster " + "state node (" + watcher
                    .getZNodePaths().clusterStateZNode + ") not found");
        }
    }

    /**
     * @return Content of the clusterup znode as a serialized pb with the pb
     * magic as prefix.
     */
    static byte[] toByteArray() {
        ZooKeeperProtos.ClusterUp.Builder builder = ZooKeeperProtos.ClusterUp.newBuilder();
        builder.setStartDate(new java.util.Date().toString());
        return ProtobufUtil.prependPBMagic(builder.build().toByteArray());
    }
}
